A combination of "Fat" and "Attitude"; the loud, boisterous, obnoxious arrogance often displayed by large and/or obese women. This is very common; many large women often try to overshadow their physical enormity with a similarly large and over-exaggerated large-and-in-charge attitude.

"Dude, that blubbery fat chick needs to shut up already. She's got a major case of fattitude."